Structure and Function of Neurons: Sensory, Relay and Motor

• Structure of a Neuron:

  > Dendrites (post-synaptic membrane)

  > Cell body and nucleus

  > Axon

  > Myelin Sheath

  > Nodes of Ranvier

  > Terminal button (pre-synaptic membrane)
• Dendrites:

  > located in post-synaptic membrane

  > where the neurotransmitter receptors are found

  > once the receptor and neurotransmitter bind, a new electrical impulse occurs
• Cell Body:

  > includes the nucleus, which contains genetic material of the cell
• Axon:

  > sends a nerve impulse (action potential) through the neuron, to transmit a message to the next neuron
• Myelin Sheath:

  > protects the axon

  > helps speed up transmission of the message
• Nodes of Ranvier:

  > speeds up transmission of the impulse by forcing it to 'jump' across gaps along the axon
• Terminal Button:

  > located in pre-synaptic membrane

  > end of the neuron

  > sends information through to the next neuron, through the release of neurotransmitters
• Sensory Neuron:

  > located in the PNS, in clusters known as ganglia

  > send information from senses (PNS) towards the brain (CNS)

  > receptors found in eyes, ears, tongue, skin

  > long dendrites and short axons

  > has myelin sheath, cell body in the middle
• Relay Neuron:

  > located in brain and visual system

  > carry nerve impulses between neurons, allowing sensory and motor neurons to communicate

  > involved in analysing sensations from these neurons and deciding how to respond

  > short dendrites and short axons

  > no myelin sheath, cell body at start
• Motor Neuron:

  > cell body in CNS, long axons form part of the PNS

  > send information via long axons from the CNS through to the effectors, such as muscles or glands

  > short dendrites and long axons

  > has myelin sheath, cell body at start